Cluster-Precursors and Self-Assembly Li36Ca4Sn24-oS64 and LiMgEu2Sn3-oS28 Crystalline Structures

Abstract

Using computer methods (the ToposPro software package), the combinatorial-topological analysis and modeling of self-assembly of the crystal structure of Li36Ca4Sn24-oS64 (space group (sg) Cmcm, a = 4.640 A, b = 27.112 A, c = 11.491 A, V = 1445.5 A3) and LiMgEu2Sn3-oS28 (sg Cmcm, a = 4.782 A, b = 20.717 A, c = 7.743 A, V = 767.1 A3). For the Li36Ca4Sn24 intermetallic compound a new type of 11-atom cluster K11 is installed, formed from double pentagonal rings: K11 = 0@11 (Li5)Ca(Sn5). The maximum cluster symmetry K11 and primary strand of translationally related K11 clusters corresponds to noncrystallographic symmetry 5m. Primary chains of linked K11 clusters preserving only symmetry m are located in the direction [100] and the distance between the centers of the clusters determines the length of vector a = 4.640 A. The layer is formed when the primary chains located antiparallel are bound. The tetrahedral clusters are located between the primary chains K4 = 0@4 (Li3Sn), forming chains in the direction [100]. The symmetry and topological code of the self-assembly processes of the 3D structure of the LiMgEu intermetallic compound LiMgEu2Sn3-oS28 is reconstructed from clusters K4 = 0@4 (LiMgEuSn) and K3 = 0@3 (Sn2Eu). The layer is formed when the parallel chains of K4 + K3 are bound.